This invention relates to a hot box sensor that can be used in combination with the patented Dot Star System (U.S. Pat. Nos. 3,929,308; 3,930,629 and 4,029,859) issued to John Armstrong et al that will apply the train brakes upon sensing an overheated wheel bearing condition. In the prior art, there are wayside monitoring systems for trains that detect wheel bearing overheating. These systems are not mounted on the train but were mounted in an infrared sensing unit mounted by the side of the rail to detect the temperature of the bearing area by infrared (hereinafter IR) waves so as to measure the wave length and thereby indicates the temperature. This system is in use commercially now and is very expensive. A typical IR detection system cost over $50,000 each. Consequently, the railroads can not afford a great number of IR wayside systems. Because of the great cost the IR detectors are rarely placed less than 25 to 50 miles apart.
The wayside system also requires a person to read the master monitor signal and issue a stop signal to the train. Therefore the wayside systems has several drawbacks: (1) the system is very expensive; (2) the system is not a continuous monitor. Wheel bearings might overheat and fail causing, derailment within a 5 or 6 mile stretch of track never having passed a wayside IR monitor; and (3) the system requires a person to make constant readings.
There is also a detector system using a plug called a "stink plug" that is presently used, in very limited numbers. This plug gives off a strong odor when the train wheel bearing overheats. When and if a conductor at the rear of the train detects the odor and stops the train or radios ahead, to stop the train.
Therefore, from a cursory review of the prior art temperature sensors it should be very clear that a continuous monitor or detector (to detect roller bearing temperature) is needed in the railroad industry.